The recent widespread application of hybridoma technology to the study of human tumors has led to the production of a large number of monoclonal antibodies directed against human tumor markers. The patterns of reactivity of these antibodies raise a number of interesting questions concerning the nature of surface antigens found on tumor cell lines, the relationship of molecules on different tumor lines to each other, and the relationship of these molecules to molecules on normal tissues. We will apply a series of immunological and protein chemical methods to obtain definitive answers to these questions. The antibodies will be used on an analytical scale for immunoprecipitation and characterization of a series of antigens by two-dimensional gel electrophoresis and peptide mapping. Immunoabsorbants will be used to isolate molecules for more detailed comparisons including amino acid sequence analysis when appropriate. The combination of newly available monoclonal antibodies and a series of advanced methods and unique instruments which have recently been developed at Caltech make this new project fully feasible. In addition, to increasing our basic understanding of the molecular and genetic nature of these molecules, this information will advance our expertise in diagnosis and therapy of human cancers.